1. Field of the Invention
The invention relates generally to manually oPerated automotive vehicle transmissions, more particularly, to a transaxle mechanism and especially to the reverse drive mechanism of a transaxle.
2. Description of the Prior Art
The reverse drive mechanism of a conventional manual transaxle includes an input shaft that carries a reverse input pinion, a reverse idler rotatably supported and slidably mounted on a reverse idler shaft, and a countershaft rotatably supporting a reverse output gear. When reverse drive operation is selected manually by the vehicle operator, his movement of the gear selector lever causes a reverse bell crank to rotate about its pivot, thereby sliding the reverse idler into engagement with the reverse input pinion and with the reverse output gear.
Generally, either the reverse input pinion or reverse output gear is formed on the periphery of a synchronizer clutch sleeve, which is moved by the vehicle operator among adjacent forward drive positions and a neutral position. When the synchronizer is in the neutral position, the reverse output gear is aligned for engagement by the reverse idler. The synchronizer clutch sleeve is formed with spline teeth on its inside surface. The clutch hub, which is fixed to the countershaft, is formed with spline teeth that are continually engaged with the spline teeth of the clutch sleeve.
The end face of the sliding idler gear, which first engages the reverse input pinion and reverse output gear, is inclined away from the gear wheels that it engages to facilitate the engagement. However, the gear teeth formed on the reverse pinion idler and reverse output gear are spur gears. Frequently, the face of the idler gear becomes damaged when a gear ratio change to the reverse drive ratio is attempted while there is relative rotation between the gear wheel and the idler. Furthermore, the gear teeth that form the torque delivery path for the reverse drive are relatively coarse in comparison to the fine teeth formed on the gear wheels and synchronizer sleeve that produce the synchronized engagement of the other gear ratios. If the gear teeth of the idler and the reverse gear wheels are not aligned, damage results in the form of flats formed on the end face of the idler when the reverse bell crank is forced by the vehicle operator to the reverse drive position. In the conventional reverse drive gear mechanism, the axis of the reverse pinion is eccentric of the axis of the reverse idler; and the axis of the reverse output gear is eccentric of the axis of the reverse idler. All of these factors contribute to the likelihood of the gear teeth crossing when reverse drive engagement is attempted while the gear teeth to be engaged are nonaligned prior to engagement.